This invention relates to a generating apparatus including a magneto acting as a power supply, and more particularly to a generating apparatus for feeding an electric power to a load including a voltage accumulating means such as a battery or the like.
A magneto has been typically used as a generator mounted on an internal combustion engine for driving a vehicle. The magneto, as widely known in the art, includes a rotor adapted to provide a magnet field by means of a permanent magnet mounted on a rotor yoke and a stator constituted of an armature core and generating coils wound on the core. The rotor is mounted on a revolving shaft of a prime mover and the stator is fixed on a mounting section provided on a casing of the prime mover, a cover thereof or the like, wherein a pole section of the armature core is rendered opposite to a pole section of the rotor through a gap of a predetermined size.
A load of the magneto or generator mounted on the internal combustion engine typically includes a battery acting as a voltage accumulating means, so that an output of the magneto is fed to the battery through a rectifying circuit. Also, the rectifying circuit typically has a smoothing capacitor connected to an output side thereof.
When such a magneto as described above is mounted on an internal combustion engine for driving a vehicle, input torque of the magneto or generator affects acceleration performance of the engine. Thus, if it is possible to suitably vary the input torque depending on traveling conditions of the vehicle, the input torque may be reduced as required, so that control which permits acceleration performance of the engine to be enhanced may be attained.
However, the magneto wherein a magnet field is provided by the permanent magnet causes an output thereof to be directly determined when a load thereof is determined, and concurrently an input thereto required is likewise determined. Thus, in the prior art, it was thought to be impossible to suitably vary an input torque of the magneto. Therefore, the prior art does not control input torque of the magneto in order to increase acceleration performance of the engine.
In view of the foregoing, in the prior art, in order to provide acceleration performance of a predetermined level while rendering the input torque required for operating the magneto at every rotational speed of the engine unvaried, the engine is designed to increase an output of the engine to the utmost. However, techniques of increasing an output of the engine are currently approaching the limitation, so that further significant improvement of the acceleration performance by design of the engine is not expected.
Also, in the prior art, when the battery is charged with a rectified output of the magneto which provides a magnet field by means of a permanent magnet, it is not possible to freely vary a charging current for the battery flowing at each of the engine speeds. Thus, when there is likelihood that an excessive charging current flows to the battery at a high rotational speed of the engine, a regulator of the output short-circuit type, which includes a short-circuit switch element for short-circuiting an output of the magneto and a control circuit for on-off controlling the switch element depending on an output of the magneto, is provided to turn on the short-circuit switch element when an output of the magneto is excessive, to thereby short-circuit an output of the magneto.
Unfortunately, use of such an output short-circuit type regulator causes a large amount of short-circuit current to flow through the short-circuit switch element, so that it is required to increase a current capacity of the switch element, leading to an increase in cost.
Also, the output short-circuit type regulator increases generation of heat from the short-circuit switch element. This requires a heat sink of a large scale in order to cool the switch element, resulting in the generating apparatus being disadvantageously large-sized.